The Triassic belt preserved in Arroio Moirão Graben, southernmost Brazil: Depositional system, sequence stratigraphy and tectonics

The influence of Gondwana tectonics in the Triassic is registered in the Arroio Moirão Graben, a relict sedimentary unit associated with the Triassic section of Paraná Basin, preserved over the Sul-Riograndense Shield. However, this graben is 150 km far from the Paraná Basin and has no clear stratigraphic correlation with the main Triassic outcropping area. Based on new sedimentological, paleontological and sequence stratigraphy analysis, we propose a sequence stratigraphy framework for the graben units and correlation with the Triassic section of Paraná Basin. The graben has a stacking of high-frequency sequences with fining upward trend, defined as flood units in a Terminal Splay model. The fossil content corresponds to the Hyperodapedon assemblage zone with Carnian age. These sequences are correlated with Candelária Sequence from Paraná Basin and represent a more proximal facies-association related with a source-area from the shield. The graben units are directly overlying the basement units and this surface registers an uplift that eroded the previous sedimentary record of Paraná basin followed by a Middle Triassic basinwide subsidence. The reactivation of inherited structures from the basement was related to the southern Gondwana orogeny in Middle to Late Triassic that controlled the deposition in the Arroio Moirão Graben.